package MyClass;
# use Class::MOP::Class
use metaclass;
# ... or use a custom metaclass
use metaclass 'MyMetaClass';
# ... or use a custom metaclass
# and custom attribute and method
# metaclasses
use metaclass 'MyMetaClass' => (
'attribute_metaclass' => 'MyAttributeMetaClass',
'method_metaclass' => 'MyMethodMetaClass',
);
# ... or just specify custom attribute
# and method classes, and Class::MOP::Class
# is the assumed metaclass
use metaclass (
'attribute_metaclass' => 'MyAttributeMetaClass',
'method_metaclass' => 'MyMethodMetaClass',
);
# if we'd rather not install a 'meta' method, we can do this
use metaclass meta_name => undef;
# or if we'd like it to have a different name,
use metaclass meta_name => 'my_meta';

This is a pragma to make it easier to use a specific metaclass and a set of custom attribute and method metaclasses. It also installs a meta method to your class as well, unless undef is passed to the meta_name option.

Note that if you are using Moose, you most likely do not want to be using this - look into Moose::Util::MetaRole instead.